1. Field of the Invention
This invention relates to a process for controlling pitch deposition from pulp in papermaking systems.
2. Description of the Prior Art
Pitch deposition can be detrimental to efficient operation of paper mills. Pitch can deposit on process equipment in papermaking systems resulting in operational problems in the systems. Pitch deposits on consistency regulators and other instrument probes can render these components useless. Deposits on screens can reduce throughput and upset operation of the system. Deposition of the pitch can occur not only on metal surfaces in the system, but also on plastic and synthetic surfaces such as machining wires, felts, foils, uhle boxes and headbox components. Pitch deposits may also break off resulting in spots and defects in the final paper product which decrease the paper's quality.
Surfactants, anionic polymers and copolymers of anionic monomers and hydrophobic monomers have been used extensively to prevent pitch deposition of metal soap and other resinuous pitch components. See "Pulp and Paper", by James P. Casey, Vol. II, 2nd edition, pp. 1096-7. Bentonite, talc, diatomaceous silica, starch, animal glue, gelatin and alum are known to reduce pitch trouble. U.S. Pat. No. 3,081,219, Drennen et al., discloses the use of a polymeric N-vinyl lactam to control pitch in the making of paper for sulfite pulps. U.S. Pat. No. 3,154,466, Nothum, discloses the use of xylene sulfonic acid-formaldehyde condensates and salts thereof as pitch dispersants in papermaking. The use of napthalene sulfonic acid-formaldehyde condensates for pitch control is also known in the art. U.S. Pat. No. 3,582,461, Lipowski et al., teaches the use of water soluble dicyandiamide-formaldehyde condensates to control pitch. U.S. Pat. No. 3,619,351, Kolosh, discloses process and composition for controlling resin in aqueous cellulose pulp suspensions which comprises incorporating in the suspension a resin control agent comprising a certain water-soluble nonsurface-active cationic quaternary ammonium salt.
Additionally, U.S. Pat. No. 3,748,220, Gard, discloses the use of an aqueous solution of nitrilotriacetic acid sodium salt and a water soluble acrylic polymer to stabilize pitch in paper pulp. U.S. Pat. No. 3,992,249, Farley, discloses the use of certain anionic vinyl polymers carrying hydrophobic-oleophilic and anionic hydrophilic substituents when added prior to the beating operation in the range of about 0.5 part to 100 parts by weight of the polymer per million parts by weight of the fibrous suspension to inhibit the deposition of adhesive pitch particles on the surfaces of pulp-mill equipment. U.S. Pat. No. 4,184,912, Payton, discloses the use of a 3-component composition comprised of 50-20% by weight of a nonionic surfactant, 45-15% by weight of an anionic dispersant, and 45-15% by weight of an anionic polymer having molecular weight less than 100,000. U.S. Pat. No. 4,190,491, Drennen et al., discloses the use of a certain water-soluble linear cationic polymer having a viscosity average molecular weight of about 35,000 to 70,000. Also, U.S. Pat. No. 4,253,912, Becker et al., discloses the use of a certain soluble, chlorine-resistant phosphonate of high calcium tolerance to disperse pitch contained in the aqueous medium of a pulp or papermaking process.